Both great packages. The Honda may be slightly underpowered but should still get on the plane with 2 or 3 on board. Its a great stowaway sib package.
Not sure exactly which Seapro you are looking at, I didnt think they inported a 350 into the UK, bit worried about engine size and weight, 25hp 4 stroke on a 3.5m sib will be heavy but very fast
I think the deciding factor for me would be how you are going to transport it, if its by trailer go for the Seapro because at over 70kg I wouldnt want to be lifting that engine. If its rolled up in a boot go for the Honda.